Electric pulse motor

ABSTRACT

The disclosure relates to an improved electric pulse motor having an arrangement wherein, with respect to a rotor element having a number of rotor-teeth, a stator assembly including a number of geometrically and electrically paired laminated U-shape stator elements is assembled based upon the conventional arrangement, but, the rotor element is provided with a specific construction for strengthening the rotor-teeth, so that radially extended rotor-teeth are reduced in axial thicknesses so as not to increase moment of inertia, making it possible to obtain a large magnetic attractice force from the stator elements so as to provide a large output torque. The stator elements are also provided with a structure and members to provide a large magnetic attractice force so that a large output torque is obtainable from the electric pulse motor.

United States Patent [191 Inaba et al.

[ 1 ELECTRIC PULSE MOTOR [75] Inventors: S'eiuemon Inaba, Kawasaki; Yo

lkebe; Sakae Yamamura, both of Tokyo, all of Japan [73] Assignee:Fujitsu Limited, Kawasaki-shi,

Japan [22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,156

[30] Foreign Application Priority Data 570,914 11/1896 Dorman ..3l0/268XVan Donselaar 310/268 Jarret et al 310/168 Primary Examiner-D. F. DugganAtt0rney-Allan Ratner 5 7 ABSTRACT The disclosure relates to an improvedelectric pulse motor having an arrangement wherein, with respect to arotor element having a number of rotor-teeth, a stator assemblyincluding a number of geometrically and electrically paired laminatedU-shape stator elements is assembled based upon the conventionalarrangement, but, the rotor element is provided with a specificconstruction for strengthening the rotor-teeth, so that radiallyextended rotor-teeth are reduced in axial thicknesses so as not toincrease moment of inertia, making it possible to obtain a largemagnetic attractice force from the stator elements so as to provide alarge output torque.

The stator elements are also provided with a structure and members toprovide a large magnetic attractice force so that a large output torqueis obtainable from the electric pulse motor.

10 Claims, 13 Drawing Figures PATENTEDJMI 8 m4 sum 1 or s lNVEN-TOR VATTORNEY PATENIEDJAI 181914 3384.850

sum 20? s INVENTOR ATTORNEY PATENTEUJAI 8 W saw 3 or 5 I NVENTORATTORNEY Pmmcnm a mu SHZET '4 OF 5 INVENTOR ATTORNEY PATENTEDJAH 8 I9743384350 saw 5 er s INVENTOR ATTORNEY ELECTRIC MOTOR The presentinvention relates to an improved construction of an electric pulsemotor.

In the conventional. construction of an electric pulse motor it isgenerally composed of rotor elements havingmany rotor teeth arranged atequal intervals on the periphery of said rotor, pairs of laminated Ushape stator elements which have many stator teeth each facing,'

the above-mentioned individual rotor teeth and are arrangedcircumferentially, each pair of said stator element receives a series ofcommand input pulses, and steps the rotor element in order.

For obtaining a large output from the rotor element in the conventionalconstruction of the electric pulse motor, it is necessary to increasethe magnetic attractive force which acts between the stator element andthe rotor element, that is, to increase. the input power which is notonly uneconomical but also increases the heat energy generated insidesaid electric pulse motor.

Another method for obtaining large output power in the conventionalconstruction is to increase the diameter of the rotor element driven bythe magnetic attractive force and thereby increase the working area ofsaid magnetic attractive force.

However, in this second method, the follow-up characteristics of theelectric pulse motor become inferior, especially, when using theelectric pulse motor as an element of a servo-system.

Also, the iron loss in the rotor element increases when the diameter ofthe rotor element is increased, and the output torque of the electricpulse motor is not proportional to the diameter of the rotor element.

To overcome the above-mentioned drawback, the method of making the rotorelement very thin while increasing the diameter of the rotor may beconsidered. However, when the rotor is made thin, the strength of therotor teeth decreases thus causing fatigue break down with the long termuse and also a vibration noise is generated in the case of high speedrevolution. As a result of this, it is necessary to strengthen the rotorteeth.

The object of the present invention relates to the provision of animproved rotor element to increase the output of the electric pulsemotor, and especially, provided with strengthened rotor'teeth thediameter of which can be increased without increasing the moment ofinertia of the rotor element.

Another object of the present invention relates to the provision ofimproved stator elements which enable increased output of the electricpulse motor to be obtained. I

Further features and advantages of the present invention will beapparent from the ensuing description with respect to the accompanyingdrawing to which, however, the scope .of the invention is no waylimited.

FIG. I is a longitudinal sectional view of the construction of theconventional electric pulse motor,

FIGS. 2, 3, 4, 5, 6 and 7 are perspective views of the embodiments ofstrengthened rotor teeth in one embodiment of the electric pulse .motoraccording to the present invention,

FIG. '8 is a longitudinal sectional view of another embodiment of theelectric pulse motor according to the present invention,

FIG. 9 is a sectional view along the line 9 9 in FIG. 8,

FIG. 10 is a longitudinal sectional view of a further embodiment of theelectric pulse motor'according to the present invention, 1

FIG. 11 is a sectional view along the line 11 11 in FIG. 10,

FIGS. 12(A) and 12 (B) are perspective views showing the laminated coresaccording to the present invention.

Referring to FIG. 1 showing the conventional electric pulse motor, therotor shaft 20 of a rotor element 21 is supported by bearings 31 whichare mounted in side plates 29 and 30. Rotor teeth 22 of the rotorelement 21 have the thickness in the axial direction and project in theradial direction and are arranged with equal pitch circumferentially.

Opening parts of stator elements 23 and 23' are disposed so as to facethe rotor element 21 and are fixed to the side plates 29 and 30 and areformed in a U shape by laminating the magnetic material strip. Magneticpoles 25 and 25 of the stator elements 23 and 23 have gaps in the axialdirection and provide a plurality of stator teeth 24 and 24' which faceeach other with equal pitch. The rotor teeth 22 of the rotor element arepositioned between the magnetic poles 25 and 25' of the stator elements23 and 23'. Stator windings 27 and 27' are provided on the leg portions26 and 26' of the pair of the stator elements 23 and 23' which face eachother and are connected in series or in parallel so as to have the sameelectrical phase. When the stator windings 27 and 27 are excited by theinput current, the magnetic flux shown by the dotted lines P in FIG. 1is generated whereby the rotorteeth 22 is the magnetic poles 26 and 26are stepped by magnetic attractive force to the position at which therotor teeth 22 and stator teeth 24 precisely face each other. A magneticspacer 32 is provided for supporting the stator elements 23 and 23'.

FIGS. 2 7 show an embodiment of the construction which strengthens thethin rotor elements which have large diameter, according to the presentinvention. Referring to FIG. 2, grooves of the rotor teeth 22 aresupported by supporting member '33 having a thichness smaller than therotor teeth 22, and said supporting member 33 is constituted in one bodywith the rotor teeth or by another member separated from the rotorteeth.

Referring to FIG. 3, the non magnetic material or resin material 34embeds the grooves of the rotor teeth to the same thickness as the rotorteeth.

FIG. 4 shows an example in which holes 35 are provided in the thinportion of the supporting member 33 shown in FIG. 2 thus decreasing theweight and the moment of inertia. FIG. 5 is an example in which furtherdecrease of the weight and the moment of the inertia of the exampleshown in FIG. 4 is achieved by shortened curved portions 36. FIGS. 6 and7 show examples in which beams 38 and 39 are provided to strengthen therotor teeth. It will be understood that the constructions shown in FIGS.2, 4, 5, 6 and 7 are constituted in the same body as the rotor elementor separately of some other material. By using the above-mentionedconstruction for strengthening the rotor elements, the dimensions of therotor elements can be increased without increasing the moment of inertiaof the rotor element or the iron loss generated in said rotor element.And thus the effective working area of the magnetic attraction and theoutput of the electric pulse motor can be increased. 7

Another example of the electric pulse motor according to the presentinvention, is shown in FIGS. 8 and 9 where the laminated U shape statorelements are im-' proved and rotor element based on the illustrations inFIG. 2 and FIGS. 4 7 are preferably used. Referring to FIGS. 8 and 9,five pairs of stator elements 43 and 43' are provided circumferentially,and four stator windings 44a, 45a, 44'a and 45'a. are provided per onepair of stator elements 43 and 43. These stator elements are connectedin series or in parallel with each other, and constitute one electricphase. Dotted line (i) in FIG. 8 show the passage of the flux generatedin the stator elements 43 and 43 in the above-mentioned electric phase.

An advantage of this embodiment is that the magnetic attraction for therotor element 41 act on the outside magnetic poles 46, 46' and on theinside magnetic poles 47 and 47 of the pair of stator elements 43 and43. Namely, as shown in FIG. 9. plural stator teeth 49a and 50a areprovided on both magnetic poles 46 and 47 of the laminated U shapestator element 43. It will be understood that plural stator teeth 49'a,50'a are provided on both magnetic poles 46' and 47 of the laminated Ushape stator element 43. Further, in this embodiment, the air gapbetween the stator elements 43 and 43' is determined by the casing 53.

The rotor teeth 42 of the rotor element 41 are preferably strengthenedas mentioned above and lengthened radially in the outward direction, andreceive a mag netic attraction force from magnetic poles 46, 46 and 47,47' of the stator elements 43 and 43. As a result of this, the torquedriving the rotor element 41 can be increased and output power greaterthan the conventional electric pulse motor can be obtained at the rotorshaft 20. As is clear from the above-mentioned explanation, in thisembodiment of the electric pulse motor,

' the output of the electric pulse motor can be increased withoutincreasing either the dimensions or the electrical input power.

A still further embodiment of the present invention is shown in FIGS. 12wherein an explanation is also given of a five phase electric pulsemotor. Referring to FIG. 10, five pairs of laminated U shape statorelements 54 and 54' which are fixed to the side plates 29 and 30 with abinding agent 62 form the stator assemblies for five phases shown by SA,SB, SC, SD and SE in FIG. 11. Cores 60 and 60 are fixed to each polepiece portion 58 and 58 of five phase stator assemblies with binding andmoulding means, and face each other via a rotor teeth 42. The advantageof this embodiment is in the addition of said cores 60 and 60 whichincrease peripherally the number of teeth and increase radially thelength of said teeth, thus increasing the magnetic attraction forcewhich is acts between the stator teeth and the rotor teeth.

Because cores 60 and 60 are also composed of laminated magnetic materialstrips they do not adversely affect the iron loss reducing property ofthe laminations in the stator elements. Referring to FIG. 10 referencenumeral 64 shows the moulding portion, and FIG. 11, 54a, 54b, 54c, 54d,54e and 60a, 60b, 60c, 60d, 60e

- show respectively the stator elements and the cores 4 shown in FIGS.12(A) and" (B). Referring to FIG. 12(A), all layers of the thin strip ofmagnetic material wound in circular roll form are bound and' ins'ulat edfrom each other with a binding agent such as synthetic resin, the statorteeth are worked by a milling machine, cores and 60 are simply dividedthe'working and the division of the stator teeth'are carried out aftermounting the roll of thin strip to the'stator; Referring to FIG. 12(8),it will be understood that the same construction as in FIG. 12(A) isobtained by laminating the thin band of the magnetic material in afan-shape. By fixing the above-mentioned cores to the magnetic polepiece portion of the stator, the effective area of the magnetic polepiece portion of the stator can be considerably increased, the numberand the radial length of the teeth can be increased, and the outputtorque generated at the rotor shaft can be considerably increased.

What is claimed is:

1. An electric pulse motor comprisingz a single rotor having a rotorshaft and a plurality of radially extending rotor teeth spaced at equaltooth pitch on a hub which is'formed unitary with said rotor teeth andismounted on the rotor shaft, said rotor further having supportingmembers, each of which is disposed between adjacent rotor teeth forproviding a physical connection between said adjacent rotor teeth; 7

side plate means comprising a pair of plates;

bearing means mounted on each said plate for rotatably supporting saidmonostage rotor between said plates;

a stator including a plurality of geometrically and electrically pairedU-shaped stator elements mounted stationary in said side plate meanswhile maintaining predetermined spaces between different paired statorelements, said paired U-shaped stator elements consisting of a pair ofU-shaped stator cores, each made of U-shaped magnetic materiallaminations, said paired U-shaped stator cores having stator teethformed on at least a pair of mutually opposing end surfaces thereof toaxially face said rotor teeth, and;

excitation winding means wound on each said stator core.

2. An electric pulse motor as claimed in claim 1, wherein said pairedU-shapedstator cores have stator teeth formed on both pairs of mutuallyopposing end surfaces thereof for providing an outer magnetic pole pairand an inner magnetic pole pair along said radially extending rotorteeth.

3. An electric pulse motor as claimed in claim 2, further comprising acylindrical casing arranged between said side plate means to define airgaps between said magnetic poles of said U-shaped stator cores and saidrotor teeth.

4. An electric pulse motor as claimed in claim 1, further comprisingcore members fixed on said pair of mutually opposing end surfaces ofsaid paired U-shaped stator cores, each of said core members being madeof radially laminated magnetic material and having a surface providedwith said stator teeth formed thereon to axially face said rotor teeth.

5. An electric pulse motor as claimed in claim 1, wherein saidsupporting members are integral of said rotor teeth.

6. An electric pulse motor as claimed in claim 1, wherein saidsupporting members are resin material decreasing weight and the momentof inertia.

9. An electric pulse motor as claimed in claim 5, wherein saidsupporting members are formed as shortened curved portions. 5

10. An electric pulse motor as claimed in claim 5, wherein saidsupporting members comprise rim-shaped beam members disposed betweensaid rotor teeth.

1. An electric pulse motor comprising: a single rotor having a rotorshaft and a plurality of radially extending rotor teeth spaced at equaltooth pitch on a hub which is formed unitary with said rotor teeth andis mounted on the rotor shaft, said rotor further having supportingmembers, each of which is disposed between adjacent rotor teeth forproviding a physical connection between said adjacent rotor teeth; sideplate means comprising a pair of plates; bearing means mounted on eachsaid plate for rotatably supporting said monostage rotor between saidplates; a stator including a plurality of geometrically and electricallypaired U-shaped stator elements mounted stationary in said side platemeans while maintaining predetermined spaces between different pairedstator elements, said paired U-shaped stator elements consisting of apair of U-shaped stator cores, each made of U-shaped magnetic materiallaminations, said paired Ushaped stator cores having stator teeth formedon at least a pair of mutually opposing end surfaces thereof to axiallyface said rotor teeth, and; excitation winding means wound on each saidstator core.
 2. An electric pulse motor as claimed in claim 1, whereinsaid paired U-shaped stator cores have stator teeth formed on both pairsof mutually opposing end surfaces thereof for providing an outermagnetic pole pair and an inner magnetic pole pair along said radiallyextending rotor teeth.
 3. An electric pulse motor as claimed in claim 2,further comprising a cylindrical casing arranged between said side platemeans to define air gaps between said magnetic poles of said U-shapedstator cores and said rotor teeth.
 4. An electric pulse motor as claimedin claim 1, further comprising core members fixed on said pair ofmutually opposing end surfaces of said paired U-shaped stator cores,each of said core members being made of radially laminated magneticmaterial and having a surface provided with said stator teeth formedthereon to axially face said rotor teeth.
 5. An electric pulse motor asclaimed in claim 1, wherein said supporting members are integral of saidrotor teeth.
 6. An electric pulse motor as claimed in claim 1, whereinsaid supporting members are resin material embedded in the spacesbetween adjacent rotor teeth so as to have the same axial thickness assaid rotor teeth.
 7. An electric pulse motor as claimed in claim 1,wherein said supporting members consist of a rim-shaped beam disposed ontops of said rotor teeth.
 8. An electric pulse motor as claimed in claim5, wherein said supporting members have openings for decreasing weightand the moment of inertia.
 9. An electric pulse motor as claimed inclaim 5, wherein said supporting members are formed as shortened curvedportions.
 10. An electric pulse motor as claimed in claim 5, whereinsaid supporting members comprise rim-shaped beam members disposedbetween said rotor teeth.